Elastic Paper with Mechanically Switchable Fiber and Pore Structure

该项目的目标是开发可可逆拉伸超过100%的纸张。随着伸长率的增加，更高的纤维排列顺序应导致板材孔隙结构的取向增加。一方面，由熵弹性驱动的变形和优先取向在施加的拉、压或剪应力结束时应立即回归；另一方面，要开发弹性纸，它最初在不施加力的情况下保持明显的伸长/压缩状态，只有在施加这种临时变形的刺激后才能恢复到初始的永久形状（即形状记忆纸）。就其化学和物理性质而言，所期望的弹性纸的纤维应与传统纸张的纤维相似，因此，唯一的区别将是新型纸张的弹性变形能力。同样，它的生产应该基于造纸技术的众所周知的组件和过程。主要的挑战是防止纸浆纤维通过氢键直接连接，而是通过纤维之间的弹性体、高度可变形的胶体颗粒间接实现它们的内聚。一方面，主要的挑战是构建具有合适尺寸、弹性、变形/松弛特性和化学结构（壳上足够数量的阳离子功能）的胶体颗粒。另一方面，纤维应具有有利于离子键形成的化学结构（如阴离子基团的附着）。最后，有必要开发一种方法，将同样具有静电稳定性的阳离子弹性体颗粒悬浮液与阴离子纸浆纤维混合，并将其转化为均匀纸，同时在颗粒和纤维表面之间形成纤维桥接离子键。在项目的后期阶段，将生产额外的胶体颗粒，它们表现出拉伸结晶或接近室温的玻璃化转变温度。通过这种方法，可以生成弹性形状记忆纸。此外，还应验证具有纤维优先取向的弹性纸是否可以开发出具有各向异性延展性的弹性纸。从角度来看，一个基本的理解，以及在理想的情况下，结构-属性关系的建模将被开发。因此，在拉伸过程中，分层孔隙结构及其取向的可变性尤为重要。

The aim of the project is to develop papers that can be reversibly stretched by more than 100%. With increasing elongation, a higher order of fiber alignment should result in an increasing orientation of the pore structure of the sheet. Deformation and preferential orientation, driven by entropy elasticity, on the one hand should immediately regress when the applied tensile, compressive or shear stress ends. On the other hand, elastic papers are to be developed, which initially retain a distinct state of elongation/compression without application of force and only return to an initial, permanent shape after application of a stimulus from this temporary deformation (i.e. shape-memory papers).With regard to their chemical and physical properties, the fibers of the desired elastic paper should be similar to those of conventional papers, hence, the only difference will be an elastic deformability of the novel paper. Likewise, its production should be based on well-known components and processes of paper making technology. The main challenge is to prevent the otherwise common direct linking of the pulp fibers by means of hydrogen bonding, and instead to achieve their cohesion indirectly via elastomeric, highly deformable colloidal particles in between the fibers.On the one hand, a major challenge is to build up the colloid particles with respect to suitable size, elasticity, deformation/relaxation characteristics and chemical structure (sufficient number of cationic functionalities on the shell). On the other hand, the fibers should be equipped with a chemical structure for preferential formation of the ionic bonds (e.g. attachment of anionic groups).Finally, it is necessary to develop a method of mixing the likewise electrostatically stabilized suspensions of the cationic elastomer particles with the anionic pulp fibers and converting them into homogeneous papers while forming the fiber-bridging ionic bonds between the particles and the surface of the fibers.In the later stage of the project, additional colloid particles are to be produced, which exhibit stretch crystallization or glass transition temperatures near room temperature. By this, elastic shape memory papers can be generated. Furthermore, it should be validated whether elastic papers with preferential orientation of the fibers can be developed for anisotropic extensibilities. Perspectively, a fundamental understanding as well as in ideal case the modeling of the structure-property relationship will be developed. Thereby, the variability of the hierarchical pore structure and its orientation during stretching is of particular importance.